Cement clinker is produced by feeding a mix of raw materials, such as limestone, into a high temperature rotating kiln. Generally, crushed raw materials are stored on site at a cement plant in raw material storage facilities, such as a raw material silo or other suitable storage means. In addition to limestone, raw materials may include clay and sand, as well as other sources of calcium, silicon, aluminum, iron, and other elements. Raw material sources may be transported from a nearby quarry or other sources.
The various raw material components are fed by a raw material feeder into a grinding and mixing facility, such as a raw mill. Raw material components may also be fed directly to a rotating kiln. The final composition of the raw mix depends on the composition and proportion of the individual raw material components. The proportion of the raw material components in the raw mix depends on the rate at which each component is fed into the raw mill or into the kiln.
The raw mix is heated in the rotating kiln, where it becomes partially molten and forms clinker minerals, or cement clinker. The cement clinker then exits the kiln and is rapidly cooled. The cooler may include a grate that is cooled by forced air, or other suitable heat exchanging means.
Clinker kiln dust may be emitted from the kiln and from the cooler, along with exhaust emissions. For example, clinker kiln dust may become suspended in the forced air used to cool the clinker exiting the kiln. The forced air may be filtered and reclaimed clinker kiln dust from the filter may be fed back into the kiln system as a raw material input.
Fuels such as coal and petroleum coke are used to feed the kiln flame to heat the raw mix in the kiln. Other fuels may include whole tires, tire chips, or other alternative fuels such as liquid wastes and plastics. Fuels may be stored at the cement plant in fuel storage containers, and fed into a fuel mill via a fuel feeder. Gaseous fuels, such as natural gas, may also be used as fuel. Gaseous fuels may be piped to the kiln, and regulated by valves or other suitable flow regulation means. A quality control operator generally monitors the rates at which fuels and raw materials are fed to the kiln.
The composition and properties of the raw materials and fuels determine the final composition of the cement clinker, and contribute to the overall efficiency of the kiln system. For example, the raw materials and fuels each have a certain moisture percentage, indicative of the amount of surface water present. Further, the raw materials each have an associated loss factor. The loss factor is indicative of the amount of water, CO2 and organic matter that exits the raw material as it reaches the high kiln temperatures. Each fuel has an associated heat value and ash factor. The heat value is indicative of the amount of heat the fuel will produce in the kiln. The ash factor is indicative of the amount of fuel ash passed through from the fuel to the final cement clinker composition.
The overall cost of the cement clinker depends on the associated costs, compositions, and properties of the individual raw materials and fuels. Thus, the final composition and total cost of the cement clinker depends on the rates at which raw materials and fuels are fed into the kiln plant system. Therefore, a system and method is needed to optimize the raw material and fuel feed rates, in order to produce a target clinker composition at a minimum cost, based upon all of the composition and efficiency data, as well as other applicable factors.